Narrow Results

In this article, we have demonstrated the investigation of scanning probe microscopy on the defects induced by slight iron contamination on p-type Si wafers with ultrathin thermal oxide layer. Using scanning capacitance microscopy (SCM) associated with atomic force microscopy, it is revealed that iron contamination induces interface traps, which significantly perturb the depletion behavior of the silicon surface. Moreover, experimental results also indicate that iron contamination leads to the lifetime decrease and the density increase of minority carriers in the defect region. From the dC/dV–V profiles, the defect region with the highest density of the interface traps also has the highest density of the deep-level traps. At a proper dc bias, the defect region clearly exhibits an obvious contrast in the SCM images.

The crystallization process of Yttria Stabilized Zirconia (YSZ) thin film and the growth process of silicon oxide (SiO_x) have been directly investigated by in-situ heating TEM method from plan-view and cross-sectional directions. The YSZ layer is crystallized by the nucleation and growth mechanism. The nucleation is started from the surface region of the YSZ layer. Ultra thin SiO_x layer on the surface of Si substrate plays an important role in the strain relaxation in the crystallization process.

The formation of nanocrystals in Zr-based alloys through three different routes, viz by rapid solidification of alloys, by crystallization of rapidly solidified metallic glasses and by crystallization of bulk metallic glasses has been described. The nanocrystal forming behaviors of rapidly solidified metallic glasses and bulk metallic glasses have been compared and contrasted. The rapidly solidified alloys, which have been examined for this purpose, are Zr₇₆Fe_24-xNi_x (x = 0,4,8,12,16,24) and Zr_69.5Cu₁₂Ni₁₁Al_7.5. In the Zr_69.5Cu₁₂Ni₁₁Al_7.5 alloy, formation of a quasicrystalline phase was observed on crystallization. Bulk glass having the composition Zr₅₂Ti₆Al₁₀Cu₁₈Ni₁₄ has been produced by copper mould casting. This has been crystallized in order to obtain nanocrystalline phases having Zr₂Ni and Zr₂Cu structures. The nanocrystalline and the nanoquasicrystalline microstructures have been examined in considerable detail in order to find out the nature of the various types of interfaces in them. Particularly the nanograin boundaries were examined by high-resolution transmission electron microscope (HREM) and their structure has been compared with that of the grain boundary in large grained material. The change in nature of these interfaces and their number with coarsening of the nanocrystal is also investigated.

We show how interfaces may be induced in materials using external fields. The structure and the dynamics of these interfaces may then be manipulated externally to achieve desired properties. We discuss three types of such interfaces: an Ising interface in a nonuniform magnetic field, a solid–liquid interface and an interface between a solid and a smectic like phase. In all of these cases we explicitly show how small size, leading to atomic-scale discreteness and stiff constraints produce interesting effects which may have applications in the fabrication of nanostructured materials.

We present the methodologies for developing high-performance thermoelectric materials using nanostructured interfaces by reviewing our three studies and giving the new aspect of nanostructuring results. (1) Connected Si nanocrystals exhibited ultrasmall thermal conductivity. The drastic thermal conductivity reduction was brought by phonon confinement and phonon scattering. Here, we present discussion about the new aspect for phonon transport: not only nanocrystal size but also shape can contribute to thermal conductivity reduction. (2) Si films including Ge nanocrystals demonstrated that phonon and carrier conductions were independently controlled in the films, where carriers were easily transported through the interfaces between Si and Ge, while phonons could be effectively scattered at the interfaces. (3) Embedded-ZnO nanowire structure demonstrated the simultaneous realization of power factor increase and thermal conductivity reduction. The $S^2\sigma$ increase was caused by the interface-dominated carrier transport. The nanowire interfaces also worked as phonon scatterers, resulting in the thermal conductivity reduction.

The interface behavior may significantly influence the mechanical properties of carbon nanotube (CNT)-reinforced composites due to the large interface area per unit volume at the composite. The modeling of CNT/polymer interfaces has been a challenge in the continuum modeling of CNT-reinforced composites. This paper presents a review of recent progress to model the CNT/matrix interfaces via a cohesive law established from the van der Waals force. A simple, analytical cohesive law is obtained from the inter-atomic potential, and is used to study the effect of CNT/matrix interfaces on the macroscopic properties of CNT-reinforced composites.

To reveal the wear mechanism of hyperbranched polysilane (HBPSi) grafted multi-walled carbon nanotubes (HBPSi–MWCNTs) modified benzoxazine–bismaleimide (BOZ–BMI) resin (HBPSi–MWCNTs/BOZ–BMI), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) were employed. The results indicated that the suitable addition of HBPSi–MWCNTs could largely enhance the tribological properties of BOZ–BMI composites. The worn surface of the composites showed that the severe wear of the BOZ–BMI resin was converted from adhesive wear to abrasive wear with the addition of HBPSi–MWCNTs. The excellent tribological properties can be attributed to the improved interfacial adhesion between HBPSi–MWCNTs and the BOZ–BMI resin matrix. The TGA demonstrated that the composite with 0.8wt.% HBPSi–MWCNTs exhibits better thermal resistance; thus, it can inhibit adhesive wear during the friction process. The XPS spectra and the surface energy showed that the HBPSi–MWCNTs could be exposed on the worn surface of the composite to improve the anti-wear capacity of the composites further.

Defects and stress distribution in the interface of Ge/Si hetero-structures play an important role in silicon-based semiconductor devices. This work at atomic scale performs molecular dynamics simulations to study the packing characteristics in the Ge/Si interface and loading features on the atoms for different contacting configurations between Ge nanopillars and Si substrates. Based on the analysis of energy, composition, the distribution of hydrostatic pressure, the Lode–Nadai parameters of each atom as well as visualized atomic packing images in the interface regions, simulation results show that contacting configurations of the Ge nanopillar with the (100) surface and the (110) surface of the Si substrate significantly affect the stability of the interface structures. The load-bearing positions of the Si surface and the inter-diffusion among the atoms in the interface regions greatly contribute to the lattice distortion of the silicon substrate, the composition, defects, and local stress distribution in the interface regions.

Metal-oxide nanoparticles with high surface area, controllable functionality and thermal and mechanical stability provide high affinity for enzymes when the next generation of biosensor applications are being considered. We report on the synthesis of metal-oxide-based nanoparticles (with different physical and chemical properties) using hydrothermal processing, photo-deposition and silane functionalization. Physical and chemical properties of the user-synthesized nanoparticles were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Raman scattering, respectively. Thus, characterized metal-oxide-based nanoparticles served as nanosupports for the immobilization of soybean peroxidase enzyme (a model enzyme) through physical binding. The enzyme–nanosupport interface was evaluated to assess the optimum nanosupport characteristics that preserve enzyme functionality and its catalytic behavior. Our results showed that both the nanosupport geometry and its charge influence the functionality and catalytic behavior of the bio-metal-oxide hybrid system.